Fuel injection valve for internal combustion engines

ABSTRACT

A fuel injection valve for internal combustion engines, having a valve body ( 1 ) in which a bore ( 3 ) is embodied that is defined on its end toward the combustion chamber by a valve seat ( 18 ) at which at least one injection opening ( 20 ) originates. The hollow valve needle ( 8 ) is located longitudinally displaceably in the bore ( 3 ) and has a valve sealing face ( 35 ) on its end oriented toward the valve seat ( 18 ). A first sealing region ( 31; 34 ) and a second sealing region ( 32; 46; 48 ) are embodied on the valve sealing face ( 35 ), and upon contact of the hollow valve needle ( 8 ) with the valve seat ( 18 ), the first sealing region ( 31; 34 ) upstream of the at least one injection opening ( 20 ) and the second sealing region ( 32; 46; 48 ) downstream of that injection opening effect sealing between the valve sealing face ( 35 ) and the valve seat ( 18 ) (FIG.  1 ).

PRIOR ART

The invention is based on a fuel injection valve for internal combustionengines, of the kind known for instance from German Patent Disclosure DE100 58 153 A1. A fuel injection valve of this kind has a valve body inwhich there is a bore that is defined on its end toward the combustionchamber by a valve seat. A pistonlike hollow valve needle is located inthe bore and on its toward the combustion chamber, that is, orientedtoward the valve seat, it has a valve sealing face with which itcooperates with the valve seat. As a result, at least one injectionopening that originates at the valve seat and, in the installed positionof the fuel injection valve, discharges into the combustion chamber ofthe engine, is opened and closed.

The fuel is typically kept on hand in a pressure chamber that isembodied between the valve needle and the wall of the bore. In thepressure chamber, at least during the injection event, a high pressureprevails, so that good atomization of the fuel is attained, which isindispensable for effective, low-pollutant combustion. Betweeninjections, the injection openings must be sealed off, however, so thatno fuel can reach the combustion chamber uncontrolled, which would leadto increased pollutant emissions. Moreover, there is otherwise the riskof so-called blowback, in which combustion gases from the combustionchamber enter through the injection openings into the injection valve,where they alter the situation such that the next injection event cannotproceed optimally. For instance, too little fuel is then injected, whichis expressed by a power drop. Moreover, the instant of injection canshift, leading to rough running and increased pollutant emissions fromthe engine.

ADVANTAGES OF THE INVENTION

The fuel injection valve of the invention having the definitivecharacteristics of claim 1 has the advantage over the prior art that theinjection openings are sealed off in the intervals between injections.To that end, on its valve sealing face, the hollow valve needle has twosealing regions; the first sealing region effects sealing between thevalve sealing face and the valve seat upstream, and the second sealingregion effects the sealing downstream, of the at least one injectionopening. The entrance to the injection openings is sealed off by bothsealing regions, so that fuel cannot reach the combustion chamberuncontrolled, nor can combustion gases from the combustion chamber enterthe fuel injection valve via the injection openings.

Advantageous features of the subject of the invention are possible bymeans of the dependent claims.

In a first advantageous features, the first sealing region is embodiedas a conical face. The result is a flat contact with the valve seat,which reduces the pressure per unit of surface area there and thusreduces the mechanical stress. The second sealing region can be embodiedin this way as well.

If the seal is to withstand high pressures, the sealing regions can beembodied by edges. To that end, the first sealing region is embodied atthe transition from a first conical face to a second conical face, andthe conical faces form part of the valve sealing face. The secondsealing region may also be embodied by an edge, preferably by providinga third conical face on the valve sealing face, between which thirdconical face and the second conical face an annular groove is embodied.At the transition from the annular groove to the third conical face, thelatter having a larger opening angle than the conical valve seat, anedge is then created that forms the second sealing region. Instead of anannular groove, it can also be provided that between two conical faces,two further conical faces are embodied, which are inclined such thatthey create an annular groove-like recess that covers the injectionopenings. Such an embodiment is easier to manufacture than a roundedannular groove, since one and the same tool can be used for all theconical faces.

It is especially advantageous if the second sealing region, which islocated downstream of the first sealing region, takes its seat on thevalve seat upon the closing motion of the valve needle before the firstsealing region does. As a result, the downstream end, toward thecombustion chamber, of the hollow valve needle, once the second sealingregion has become seated on the valve sealing face, must deformelastically somewhat inward, which then makes it possible for the firstsealing region to take its seat. The result is a high pressure per unitof surface area in both the first and the second sealing region and thusa very secure sealing of the injection openings. To facilitate thiseffect and to enable good elastic deformability, a concave feature bywhich an elastic sealing lip is formed can be provided downstream of thefirst sealing region on the hollow valve needle. The second sealingregion is embodied on the sealing lip and takes its seat on the valveseat before the first sealing region. The sealing lip is easilyelastically deformable, which on the one hand assures good sealing andon the other does not cause excessive deformation or strains of thehollow valve needle.

DRAWING

Various exemplary embodiments of the fuel injection valve of theinvention are shown in the drawing.

FIG. 1 shows a longitudinal section through a fuel injection valve ofthe invention;

FIG. 2 is an enlargement of the detail marked II in FIG. 1;

FIG. 3 is an enlargement of the detail marked III in FIG. 2;

FIG. 4, FIG. 5, FIG. 6, FIG. 7, and FIG. 8, each in the same view asFIG. 3, show further exemplary embodiments.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

In FIG. 1, a fuel injection valve is shown in longitudinal section. In avalve body 1, a bore 3 is embodied that is defined on its end toward thecombustion chamber by a conical valve seat 18. External injectionopenings 20 and internal injection openings 22 originate at the valveseat 18 and are located at different levels relative to the longitudinalaxis 7 of the bore 3. In general, a plurality of injection openings areprovided over the circumference of the injection valve, with all theouter injection openings 20 and all the inner injection openings 22located at the same level relative to the longitudinal axis 7 of thebore 3, forming two rows of injection openings. The injection openings20, 22, in the installed position of the fuel injection valve, dischargeinto the combustion chamber of the engine.

A hollow valve needle 8 is located longitudinally displaceably in thebore 3 and is guided sealingly in a guide portion of the bore 3 facingaway from the combustion chamber. Beginning at the guided portion, thehollow valve needle 8 tapers toward the valve seat 18, forming apressure shoulder 12, and on its end toward the combustion chamber andthe valve seat 18, it changes over into a valve sealing face 35, whichis embodied substantially conically and by which the hollow valve needle8 cooperates with the valve seat 18. A pressure chamber 14 is embodiedbetween the hollow valve needle 8 and the wall of the bore 3 and isradially enlarged in a region adjoining the guide portion. An inletconduit 16 extending within the valve body 1 discharges into the radialenlargement of the pressure chamber 14, and by way of this conduit thepressure chamber 14 can be filled with fuel at high pressure.

The hollow valve needle 18 has a longitudinal bore 11, which is embodiedconcentrically with the longitudinal axis of the hollow valve needle 18and extends over the entire length thereof. In the longitudinal bore 11,a valve needle 10 is located longitudinally displaceably; on its endtoward the combustion chamber, it has a valve sealing face 42, by whichthe valve needle 10 cooperates with the valve seat 18 for controllingthe inner injection openings 22. In the longitudinal bore 11, the valveneedle 10 is guided near the valve seat 18 in a guide portion 27, whichis formed by a slight thickening of the valve needle 10. Both the hollowvalve needle 8 and the valve needle 10 are subjected, on their endfacing away from the combustion chamber, to a closing force that pointsin the direction of the valve seat 18 and that is generated for instanceby one spring per needle, or by a hydraulic device.

FIG. 2 shows an enlargement of the detail marked 11 in FIG. 1. Thehollow valve needle 8 cooperates with the valve seat 18 in such a waythat upon contact of the hollow valve needle 8 with the valve seat 18,the outer injection openings 20 are closed. In a similar way, the valveneedle 10 closes the inner injection openings 22 upon contact with thevalve seat 18.

The function of the fuel injection valve is as follows: At the onset ofthe injection cycle, both the hollow valve needle 8, with its valvesealing face 35, and the valve needle 10, with its valve sealing face42, are in contact with the valve seat 18. In the pressure chamber 14, ahigh fuel pressure already prevails, by which a hydraulic opening forceon the pressure shoulder 12 of the hollow valve needle 8 is produced. Ifthe injection is to begin, the closing force on the hollow valve needle8 is reduced, so that now the hydraulic opening force predominates overthe closing force. This produces a resultant force on the hollow valveneedle 8 that moves it away from the valve seat 18. The outer injectionopenings 20 are thus uncovered, and fuel can flow out of the pressurechamber 14 between the valve sealing face 35 and the valve seat 18 tothe outer injection openings 20 and is injected through them into thecombustion chamber. Initially, the valve needle 10 remains in itsclosing position, in which the inner injection openings 22 are closed.Since until now, only some of the injection openings 20, 22 have beenopened, the fuel is injected at a relatively low rate, which is requiredfor instance for a preinjection. Once the hollow valve needle 8 liftsfrom the valve seat 18, the valve needle 10 is subjected to fuelpressure, so that a hydraulic opening force oriented counter to thecorresponding closing force is also produced on the valve needle 10. Assoon as the opening force predominates, the valve needle 10 also movesaway from the valve seat 18, as a result of which the inner injectionopenings 22 are uncovered. Now fuel is injected through all theinjection openings 20, 22 at a considerably higher rate, of the kindrequired for instance for the main injection.

Provision can also be made for the closing force on the hollow valveneedle 8 to remain constant at all times. In that case, the fuelpressure in the pressure chamber 14 is not increased until before theonset of the injection, until the rising fuel pressure caused by thehydraulic forces on the hollow valve needle 8 predominates over theclosing force. Alternatively, provision may be made for the valve needle10 to remain closed as the result of a suitably strong closing force,and for the hollow valve needle 8 after opening to slide back into itsclosing position. Such an injection is for instance required for apreinjection or pilot injection that is chronologically separate fromthe main injection.

FIG. 3 shows an enlarged detail of the hollow valve needle 8 in theregion of the valve sealing face 35, this being the detail marked III inFIG. 2. The valve sealing face 35 has a first conical face 30, a secondconical face 31, and a third conical face 32, which are embodied in thatorder in the downstream direction on the valve sealing face 35. Thefirst conical face 30 is directly adjacent the second conical face 31,so that an edge 34 is embodied at the transition. The opening angle a₁of the first conical face 30 is smaller than the opening angle a₂ of thesecond conical face 31. The opening angle a₃ of the third conical face32 is equal to that of the second conical face 31, and both conicalfaces 31, 32 are located on a common imaginary conical surface. Betweenthe second conical face 31 and the third conical face 32, an annulargroove 37 is embodied, whose upstream edge 45 and downstream edge 46,upon contact of the valve sealing face 35 with the valve seat 18, arelocated upstream and downstream, respectively, of the outer injectionopenings 20. The valve seat 18 is likewise embodied conically and has anopening angle b, which is equal to the opening angle a₂ of the secondconical face 31 and the opening angle a₃ of the third conical face 32.As a result, in the closing position of the hollow valve needle 8, boththe second conical face 31, which forms the first sealing region, andthe third conical face 32, which forms the second sealing region, comeinto contact with the valve seat 18, so that the outer injectionopenings 20 are sealed off from the pressure chamber 14 and downstreamin the direction of the inner injection openings 22. Since the annulargroove 37 is embodied as relatively shallow, and the two sealing regionsof the valve needle 8 seal off the annular groove 37 adequately, only aslight fuel volume that can reach the combustion chamber when the fuelinjection valve is closed is produced via the outer injection openings20.

FIG. 4 shows the same view as FIG. 3 for a further exemplary embodiment.Here, however, the second conical face 31 has an opening angle a₂ thatis greater than the opening angle b of the conical valve seat 18. As aresult, the edge 34, located at the transition from the first conicalface 30 to the second conical face 31, is embodied as a sealing edge andforms the first sealing region. The third conical face 32 is unchangedfrom the exemplary embodiment shown in FIG. 3.

The edge 34 and the third conical face 32, that is, the two sealingregions, are located relative to the valve seat 18 in such a way thatwhen the fuel injection valve is new, the edge 34 rests on the valveseat 18 first, while the third conical face 32 is still spaced apartfrom the valve seat 18, but only by a very narrow gap, which producesadequate but not complete sealing. In operation, the edge 34 is hammeredinto the valve seat 18 somewhat until the third conical face 32, in theclosing position of the hollow valve needle 8, rests on the valve seat18, so that sealing with high pressure per unit of surface area thusresults in both sealing regions, thus producing good sealing in thefirst sealing region, which seals off from the high pressure of thepressure chamber. However, provision may also be made that in the newfuel injection valve both sealing regions are oriented in such a waythat the hollow valve needle 8 first becomes seated on the valve seat 18with the second sealing region, that is, the third conical face 32. Bythe cooperation with the valve seat 18, the hollow valve needle isdeformed elastically inward somewhat in the region of the third conicalface 32, to an extent such that the edge 34 is seated on the valve seat18. Thus once again suitable sealing both upstream and downstream of theouter injection openings 20 is produced.

A further exemplary embodiment is shown in FIG. 5, in the same view asin FIG. 3. Here, both the opening angle a₂ of the second conical face 31and the opening angle a₃ of the third conical face 32 are larger thanthe opening angle b of the conical valve seat 18. The downstream edge 46of the annular groove 37 here forms the second sealing region, whichrelative to the first sealing region, that is, the edge 34, is embodiedsuch that either the first or the second sealing region comes to restfirst on the valve seat 18. If the first sealing region, that is, theedge 34, comes to rest first, then the complete sealing at the secondsealing region comes about only in operation, in which the edge 34 ishammered somewhat into the valve seat 18 until the downstream edge 46 ofthe annular groove 37 rests on the valve seat 18. Conversely, if thesecond sealing region, that is, the downstream edge 46, comes to rest onthe valve seat 18 first, then the first sealing region, as in theexemplary embodiment shown in FIG. 4 and described above, providessealing when the hollow valve needle 18 becomes deformed elasticallyinward at its tip.

FIG. 6 shows a further exemplary embodiment in the same view as in FIG.5. The opening angle a1 of the first conical face 30 is smaller than theopening angle b of the conical valve seat 18, so that an upstream edge45 that forms the first sealing region is formed at the transition fromthe first conical face 30 to the annular groove 37. The downstream edge46 of the annular groove 37 is embodied as a second sealing region,which is adjoined by a convex end portion 39. The cooperation betweenthe upstream edge 45 and the downstream edge 46 of the annular groove 37is analogous to the exemplary embodiment of FIG. 5. Accordingly, it canbe provided either that the upstream edge 45 rests on the valve seat 18before the downstream edge 46, or vice versa.

A further exemplary embodiment is shown in FIG. 7. Besides the firstconical face 30 and the third conical face 32, which are locatedidentically to the conical faces in FIG. 5, the valve needle 8 has,instead of an annular groove, an upper conical face 31 a and a lowerconical face 31 b. At the transition from the first conical face 30 tothe upper conical face 31 a, the first sealing region is embodied, inthe form of an upstream edge 45, and correspondingly, a downstream edge46 that forms the second sealing region is embodied at the transitionfrom the lower conical face 31 b to the third conical face 32. Theadvantage of this arrangement is its ease of manufacture, since all theconical faces on the valve needle 8 can be ground with the same tools.The sealing functions at the first and second sealing regions areanalogous to the exemplary embodiment shown in FIG. 5.

The sealing at both sealing regions by elastic deformation of the hollowvalve needle 8 is also the principle in the exemplary embodiment shownin FIG. 8, in which the identical parts of the hollow valve needle areidentified by the same reference numerals as in FIGS. 3, 4, and 5. Here,instead of the annular groove 37 and the third conical face 32, aconcave feature 50 is provided, by which a sealing lip 52 is formed. Asealing edge 48 that forms the second sealing region is provided on thesealing lip 52. As a result of the concave feature, the sealing lip 52is embodied as relatively thin, resulting in good elastic deformability.As already noted above, the sealing principle is due to the fact that inthe closing motion of the hollow valve needle 8, the sealing edge 48takes its seat on the conical valve seat 18 first. As a result of thecontact pressure of the hollow valve needle 8 against the valve seat 18,the sealing lip 52 is deformed elastically inward, until the edge 34,which analogously to the exemplary embodiment shown in FIG. 5 isembodied between the first conical face 30 and the second conical face31, takes its seat on the valve seat 18.

1. A fuel injection valve for internal combustion engines, having avalve body (1) in which a bore (3) is embodied that is defined on itsend toward the combustion chamber by a valve seat (18) at which at leastone injection opening (20) originates, and having a hollow valve needle(8), which is located longitudinally displaceably in the bore and whichhas a valve sealing face (35) on its end oriented toward the valve seat(18), characterized in that a first sealing region (31; 34) and a secondsealing region (32; 46; 48) are embodied on the valve sealing face (35),and the hollow valve needle (8) cooperates with the valve seat (18) insuch a way that upon contact of the hollow valve needle (8) with thevalve seat (18), the first sealing region (31; 34) upstream of the atleast one injection opening (20) and the second sealing region (32; 46;48) downstream of that injection opening effect sealing between thevalve sealing face (35) and the valve seat (18).
 2. The fuel injectionvalve according to claim 1, characterized in that the first sealingregion (31; 34) is embodied as a conical face (31), which upon contactof the hollow valve needle (8) with the valve seat (18) rests flatlythereon.
 3. The fuel injection valve according to claim 1, characterizedin that downstream of the conical face (31), a concave feature (50) isprovided on the hollow valve needle (8), forming a sealing lip (52) onwhich the second sealing region (48) is embodied, and the sealing lip(52) is deformable elastically inward.
 4. The fuel injection valveaccording to claim 1, characterized in that the second sealing region(31; 34) is embodied as a conical face (32), which upon contact of thehollow valve needle (8) with the valve seat (18) rests flatly thereon.5. The fuel injection valve according to claim 1, characterized in thatan annular groove (37) extending all the way around is embodied on thevalve sealing face (35) between the first sealing region (31; 34) andthe second sealing region (32; 46).
 6. The fuel injection valveaccording to claim 6, characterized in that the annular groove (37)covers the at least one injection opening (20).
 7. The fuel injectionvalve according to claim 6, characterized in that the first sealingregion (45) is formed by the upstream edge (45) of the annular groove(37), which forms the boundary line between a first conical face (30)and the annular groove (37).
 8. The fuel injection valve according toclaim 6, characterized in that the second sealing region (32; 46; 48) isformed by an edge (46) which is embodied at the transition from theannular groove (37) to the part of the valve sealing face (35) locateddownstream of the annular groove (37).
 9. The fuel injection valveaccording to claim 8, characterized in that the part of the valvesealing face (35) located downstream of the annular groove (37) isembodied as a convex end portion (39).
 10. The fuel injection valveaccording to claim 1, characterized in that the valve sealing face (35)has a first conical face (30), a second conical face (31) locateddownstream of the first conical face (30), and a third conical face (32)located downstream of the second conical face (31).
 11. The fuelinjection valve according to claim 10, characterized in that the firstconical face (30) has a smaller opening angle than the second conicalface (31), so that at the boundary line between the conical faces (30;31), the first sealing region is embodied as an edge (34) extending allthe way around.
 12. The fuel injection valve according to claim 10,characterized in that the third conical face (32) has a larger openingangle than the conical valve seat (18).
 13. The fuel injection valveaccording to claim 10, characterized in that an annular groove (37) thatcovers the injection openings (20) is formed between the second conicalface (31) and the third conical face (32).
 14. The fuel injection valveaccording to claim 1, characterized in that the valve sealing face (35)includes a first conical face (30), an upper conical face (31 a) locateddownstream of the first conical face (30), a lower conical face (31 b)located downstream of the upper one, and a third conical face (32)located downstream of that, the first sealing region being formed by theedge (45) between the first conical face (30) and the upper conical face(31 a) and the second sealing region being formed between the lowerconical face (31 b) and the third conical face (32).
 15. The fuelinjection valve according to claim 1, characterized in that the secondsealing region (32; 46; 48) comes to rest on the valve seat (18) beforethe first sealing region (31; 34), upon the motion of the hollow valveneedle (8) toward the valve seat (18).
 16. The fuel injection valveaccording to claim 1, characterized in that a valve needle (10) islocated longitudinally displaceably in the hollow valve needle (8) andcontrols the opening of at least one further injection opening (22),which originates at the valve seat (18).
 17. An internal combustionengine having at least one combustion chamber and at least one fuelinjection valve through which fuel can be injected into the combustionchamber, characterized in that the fuel injection valve is embodied inaccordance with claim 1.